The present invention relates to a process and an apparatus for collecting and stapling folded printed sheets of the type having a plurality of supports which travel along a closed path of conveyance, on which supports printed sheets can be deposited astride one another and a stapling station for placing staples onto the printed sheets on the supports.
Such an apparatus is known, for example, from DE-OS 3,616,566, or from the corresponding U.S. Pat. No. 4,735,406. This disclosed apparatus has a collector drum with saddle-shaped supports that are arranged parallel to a common axis of rotation and are driven to rotate about this axis. Provided in the direction of the axis of rotation are two feeders which follow one another and deposit folded printed sheets onto the supports. A stapling station follows the feeders for stapling together the mutually overlying printed sheets. Immediately after stapling, the collected and stapled printed sheets are deposited onto a conveyor belt which transports the stapled printed sheets away. The stapling station has a plurality of stapling head pairs, which are arranged at the spacing of the supports, which extend parallel to one another, on a bail that is swivelably mounted on the axis of rotation of the drum. The bail is moved to and from by means of a swivel drive with the stapling heads simultaneously placing one staple each into the printed sheets during the synchronous operation with the supports.
As to the construction of the stapling heads, these above-referenced printed publications refer to CH Patent Specification 549,443 or U.S. Pat. No. 4,614,290. These known stapling heads are each fed a wire from which a wire section is severed in each case by means of a cutting device arranged on the stapling head. This wire section is bent around a matrix by means of a slidably mounted stamp to form a staple. The staple is forced out of the stamp by means of a slidably mounted ram and inserted into the printed sheets. This known apparatus has the disadvantage that the stapling station must have a complicated drive which must apply large accelerating forces, especially in the case of a high processing rate. Moreover, during each operational cycle of the stapling station, the movement of the stapling heads must be exactly synchronized with the supports. Since a wire has to be fed to each stapling head, in the case of moving stapling heads this synchronization is complicated both for the feeding of the wire and for the stapling heads themselves.
A stapling station for stapling together printed sheets carried by a rotating cylinder is described in EP-A 0,205,144 and corresponding U.S. Pat. No. 4,750,661. Three stapling heads are arranged next to one another in each case at the free ends of a cruciform holding device. The holding device is driven to rotate opposite to the direction of rotation of the cylinder about a shaft parallel to the axis of the cylinder. The three stapling heads run past three wire section dispensers common to all corresponding stapling heads. The circular track of travel of the stapling heads is tangent to the surface of the cylinder. The rotary motion of the holding device is synchronized with the cylinder in such a way that the printed sheets to be stapled to one another always meet the stapling heads. In this known stapling station, only an exceptionally short time is available in each case for placing the staples. This renders reliable, good quality stapling difficult in the case of high processing rates.
Furthermore, an apparatus for collecting folded printed sheets is known from CH Patent Specification 645,074 and corresponding U.S. Pat. No. 4,408,755. This apparatus likewise has a drum with supports extending parallel to a common axis of rotation. The folded print.RTM.d sheets are deposited one above the other, mutually associated to form zigzag volumes, on the supports. By means of a stapling station (not described in more detail), staples are placed in the volumes which are laid one above the other and supported by the supports.
Therefore, it is an object of the present invention to create a process according to the generic type described above for collecting folded printed sheets, and to provide a corresponding stapling apparatus in which the stapling station has a high processing capacity yet has simply constructed stapling heads and a relatively uncomplicated drive.